Company brochures No. 274e/3.05/15 and 274e/4.05/10 of Lurgi AG, Frankfurt am Main, describe directly contacting vegetable oils or animal fats with steam in counterflow in a splitter column at a temperature of 260° C. and a pressure of 55 bar[a] and thereby produce fatty acids and sweet water containing 12 to 25 vol-% glycerol. For recovering the glycerol, the sweet water purified from dissolved fats and proteins is concentrated by multistage evaporation of the water to obtain raw glycerol containing about 88 vol-% glycerol and subsequently the raw glycerol possibly is concentrated by distillation at a vacuum of about 15 mbar[a] and a temperature of about 160° C. to obtain 92 to 95 vol-% glycerol. The fatty acids produced by splitting the oils or fats are separated into a top fraction and a middle fraction by two-stage distillation; wherein monoglycerides, diglycerides and salts accumulate in the bottom as impurities. Both fatty acid fractions are intensively mixed in a stirred reactor by adding fatty alcohol at a temperature of about 250° C. and at atmospheric pressure for a period of 12 hours on average, with the reaction water being discharged continuously. The ester bonds of the triglycerides of the oils or fats are separated and wax ester is obtained, from which fatty alcohol subsequently is generated by hydrogenating at a pressure in the range from 200 to 270 bar[a] and a temperature in the range from 240 to 330° C. The reaction product obtained upon esterification is cooled and thereby separated into hydrogen and raw fatty alcohol. The hydrogen is again used for hydrogenating the wax ester on a fixed-bed catalyst of copper-chromium oxide catalyst particles. Part of the raw fatty alcohol is recirculated into the stirred reactor for esterification of the fatty acids and the other part is charged to a rectification column, for example, for producing pharmaceutical glycerol.
In the process for producing fatty alcohol as described in EP 0737664 B1, a liquid intermediate product consisting of at least 50 wt-% wax ester is produced from a liquid starting mixture containing fatty acid at temperatures of 120 to 320° C. and pressures of 20 to 400 bar[a], which is hydrogenated by adding hydrogen and by admixing fine grain catalyst, and a raw product consisting of at least 75 wt-% fatty alcohol is formed. From the raw product a partial stream containing fatty alcohol is separated and added to the liquid starting mixture. The hydrogenation of fatty acid methyl ester in the gas phase requires a separate circuit.
DE 3425758 C2 describes a process for producing alcohols by hydrogenating compounds with the corresponding number of carbon atoms with an acid, ester or aldehyde function. The hydrogenation is performed at a hydrogen pressure in the range from 20 to 100 bar and at a temperature in the range from 150 to 300° C. in the presence of a catalyst consisting of a mixture of copper and chromium with about 20 to about 40 wt-% copper (calculated as oxide) and a copper component present on a carrier with about 5 to about 45 wt-% copper.
EP 0454704 B1 describes a process for producing fatty alcohols from fatty acid with a lower alkanol by forming the corresponding lower ester, in which the ester is hydrogenated to obtain fatty alcohol in the presence of a catalyst at a temperature in the range from 80 to 140° C. and a pressure in the range from 0.1 to 25 bar. The hydrogenation product is subjected to a transesterification by using an acid ion exchange catalyst in order to convert the non-reacted ester of the hydrogenation product to wax ester by reaction with the fatty alcohol. Non-reacted alkanol is evaporated from the mixture and the remaining mixture is distilled, so that a fatty alcohol free from ester is produced as top product and a distillation residue containing fatty alcohol and wax ester is obtained.